The conventional engine ignition cable, connected between the coil, the distributor and the spark plug, is generally made of high electro-conductive metal wire such as copper, and such ignition cables have many advantages. The high conductive metal has low electro-resistance, and can apply the high current generated by the coil to the spark plug, thereby producing powerful sparks which produce excellent ignition capability for the engine.
However, the conventional engine ignition cable has several drawbacks, namely the generation of high frequency noise which adversely effects the electronic components of the automobile, such as the radio, wireless communication components, or the TV. Such high frequency noise is caused by the high current which flows in the high voltage circuit between the ignition coil and the spark plug.
Due to the above mentioned problems, an ignition cable made of metal material cannot be used in many countries and, moreover, the ignition cable material is regulated and uniform by the standards of each country, for example the KS, JIS, SEA and ASTM standards.
The Korean standard (KS), Japan Industrial standard (JIS), and the ASTM standard sets limits on the electro-resistant value of the ignition cable to below 16 Kohm/m, and they rule that the ignition cable is made of a high polymer material. However, the high polymer electro-conductive material which constitutes the conventional ignition cable has several drawbacks in the starting time of the engine.
Generally, the conventional ignition cables can be classified into five groups as shown in FIG. 3:
The fabrication and component parts of the above categories of conventional ignition cables are as follows:
______________________________________ D + G portion: 1. Mix electro-conductive carbon black (CC) with rubber. 2. Mix carbon black with synthetic resin. G portion: 1. Dip electro-conductive carbon black (anti-tension part) in glass fiber in order to raise conductivity, or use glass fiber only. 2. Mix electro-conductive carbon black with aramide fiber or use aramide fiber only E portion: Use magnetic rubber for preventing the generation of the high fre- quency noise and extend the length of the cable by winding 0.2 mm- thick metal wire (F) on E portion. A + B portion: Composed of non-conductive rubber. C portion: Weave with glass fiber which serves as the anti-tension part of the cable. ______________________________________
The conventional carbon black is normally used as the electro-conductive material, that is: the conventional acetylene carbon black is used to raise the electro-conductivity. Said acetylene carbon black, consisting of a low molecular weight material, is made by mixing carbon black with rubber and/or synthetic resin. However, the electro-conductivity of the conventional carbon black has a critical value because of a property of matter such as strength and aging characteristics.
That is, if a large amount of carbon black is mixed with rubber or synthetic resin, the property of matter are poor, while on the contrary the electro-conductivity rises. For example, adding a large amount of carbon black results in very poor aging characteristics, as well as expediting the oxidation phenomenon. Also, the bending power of the cable is substantially reduced so that the cable is easily broken and/or very weakened from physical shock.
Moreover, as is apparent in the case where the cable is broken, electricity is not conducted and the function of the ignition cable is lost. Accordingly, because it is difficult to maintain an electro-resistance value of 16 Kohm/m by mixing the carbon black with rubber or synthetic resin, the carbon black is dipped in the aramide fiber, or glass fiber, of the anti-tension part (the G portion) in order to raise conductivity of the ignition cable.
Additional problems with conventional ignition cables include the fact that the electro-conductivity cannot rise satisfactorily because the resistance value of the ignition cable cannot be dropped below 16 Kohm/m. Also, the higher the voltage which is generated from the ignition coil, the resultant higher electro-resistance results in greater adverse aging of the conductive rubber. Moreover, as the electro-resistance becomes higher than 16 Kohm/m, the current is not satisfactorily supplied to the spark plug, and the spark supplied by the spark plug is weakened. This results in the fuel in the cylinder being unsatisfactorily ignited and imperfect combustion gases being emitted in the air. This, of course, causes contamination of the air, as well as a loss of fuel.
It is, therefore, an object of the instant invention to solve the above mentioned problems, while at the same time providing an ignition cable that prevents the occurrence of high frequency noise in a gasoline engine.